Propeller template



April 1953 v. s. DRAKE PROPELLER TEMPLATE Filed Dec. 2, 1947 Fig.4

INIfEZNTOR. Vaslll .5. Brake Fig.3

Fig.2

Attorney Patented Apr. 28, 1953 UNITED STATES PATENT OFFICE 2,636,280PROPELLER TEMPLATE VasililS. Drake, San Diego, slalif.v

Application Decemher 2, 1947, Serial No. 789,260

(Granted under Title 35, U. S. Code (1952),

sec. 266) 4 Claims.

This invention relates to propeller blade templates, and moreparticularly to an adjustable template which may be employed in thechecking of practically all types of propeller blades.

In the fabrication and repair of propeller blades it is essential thatthe pitch of the blade at various points along the length thereof bedetermined accurately. This Operation is performed, on a demountedpropeller, by securing thepropeller to a table, with the propeller shaftvertical and the blade to be checked extending over and above thesurface of the table. A pro tractor is then positioned a predetermineddistance away from the shaft axis, and the inclination of the propellersurface, on a line normal to the blade axis, is measured. Thisinclination, known as propeller pitch, is measured at prede terminedradii from the propeller shaft, in accordance with a standard tableestablished by the propeller designer.

When the under face, i. e. that facing the table, of the blade is formedof a straight line generatrix, a simple protractor having a straightabutting edge may be used. When, however, the under face of the plate iscurved in accordance with air foil considerations, means must beinterposed between the protractor straight edge and the propeller faceto insure that the protractor edge will be exactly parallel to a linethrough the center of the propeller section.

It is an object of the instant invention to provide a template whichmaybe positioned against a propeller blade to derive a straight edgewhich will be exactly parallel to the center line of the propellersection, and which may be used on propellers having differing contours.

It is another object of this invention to provide a universal templatewhich may be used in pitch measurements of practically all types ofpropellers manufactured.

It is a further object of this invention to provide a template ofsimplified and rugged construction which may be mountedon a protractorfor pitch measurement of practically any type of propeller.

In accordance with the instant invention, the template is constructedhaving three points of abutment against a propeller, thereby providingpositive yet unambiguous positioning of the template against thepropeller. Two of the points are relatively fixed and permanent; thethird point is variable, thereby adapting the template for use withpractically any known type of propeller. This third abutment point ispart of an adjustable abutment holder which is so through one of theplates 23.

dices 28 are marked along the barl3 cooperable' mounted on the templatethat the third abutment point has two degrees of adjustability, i. e.may be adjusted both longitudinally and transversely of the template.

'I'wo exemplary embodiments of the instant invention will now bedescribed with reference to the accompanying drawing, wherein:

Fig. .1 shows a first embodiment of the instant template mounted on aprotractor and applied to a propeller. Fig. 1 is taken generally alongline. l-l of Fig. 2;

Fig. 2 is a plan view showing more generally how the template is appliedto the propeller;

Fig. 3 is an enlarged detailed View, showing an alternative type ofabutment member constituting the third or variable abutment surface;andv Fig. 4 is a section taken along line l4 of Fig. 8.

Referring to the drawing, H designates the cross section of a propellerblade, against which pressed the template 12, comprising a bar It havingat one end thereof a transverse abutment post it forming an abutmentsurface for the leading edge l5 of the propeller II. A second abutmentsurface or point is formed of a button 16 mounted at the edge of a stepportion I? positioned at the intersection of the bar 13 and the post 14.If desired, the parts l3, M, and I? may be made integral, although it ispreferred to form the button It of a separate piece so that it may befabricated to closer tolerance.

The two points of abutment thus described require only a third abutmentpoint, spaced there from, to assure that the template may be placed inpositive yet unambiguous position against the propeller il. In the Fig.1 embodiment this third point is provided by a-cam 2| fixed to ashaft 22journaled between a pair of plates 23 which embrace the bar I3 andconstitute a slider 24 longitu dinally adjustable along the bar. Theplates 23 protrude transversely above and below the bar l3,

Slider 24 may be moved back and forth along the barl3 and locked inpre-selected position by means of a set screw or locking screw 21threaded Transverse inwith one of the edges, e. g. edge 29, of theslider 24 to aid in positioning the slider along the bar. One degree ofpositioning of the abutment point 26, i. e. longitudinally of the bar[3, is thus determined.

The other degree of positioning of the abutment point 26, i. e.transversely of the bar I3, is determined in discrete steps by theprovision of a series of recesses 3| in the outer surface of one of theplates 23, disposed circumferentially adjacent the end of the crank 25,which is provided with a suitable form of spring pressed detent (notshown) engageable in the recesses 3|.

The lower protruding portions 33 of the plates 23 constitute abifurcated bracket, which may be fitted over a protractor bar 34 andfirmly afiixed thereto by a set screw 35, threaded through one of theplates 23. A similar mounting arrangement is provided adjacent other endof thebar l3 in the form of a pair of mounting plates 36 fixedly securedto the bar l3 and embracing the protractor bar 34, to which they may beselectively locked by a set screw 31.

Operation The manner of use of the protractor illustrated in Fig. 1 willnow be described, with reference to Figs. 1 and 2.

The propeller 4| to be checked is mounted with its shaft 42 vertical andwith one of the blades ll extending over the surface of a table 43. At apredetermined radius from the shaft 42, determined by the specificationsof the propeller designer, the template I2 is positioned beneath theblade ll. Prior to this step the slider 24 has been locked by set screw21 at the proper index 28, as prescribed by the propeller designer.Likewise, the end of the crank 25 has been set in the proper recess 3 I,pursuant to designers requirements, thus placing the upper surface ofthe cam 2| as predetermined distance from the bar [3. The third abutmentpoint 26 has thus been disposed, in accordance with the requirements ofthe propeller designer, so that for the particular propeller ll beingmeasured, the section center line 44 of the propeller II will be, whenall three abutment points are engaged, exactly parallel to theprotractor bar 34, when the template [2 is mounted thereon.

After positioning the template l2 against the propeller II, the operatormoves the protractor 45, including its protractor bar 34, into positionand clamps it to the template I2, now employing the set screws and 31,Height adjustability of the protractor above the table 43 may beaccommodated by suitable means such as telescoping of the protractorstandard as shown at 46. The blade H is then checked at each of theseveral prescribed radii, the transverse and longitudinal settings ofthe abutment point 26 being varied as specified.

The blade I I may be, and is generally, checked while mounted to theairplane. The instant device is equally suitable for such operation. Inthis case a protractor adapted for use on a mounted propeller isemployed. An example of such a protractor is illustrated in WhitechesterPatent 2,383,527. The instant template is inserted between the straightedge of the Whitechester protractor and the curved blade contour, in amanner similar to that described immediately above.

Modification The manner for achieving transverse adjustability of thepoint 26 shown in Fig. 1 is only one of several suitable arrangementsthat may be employed. Another satisfactory way of achieving the sameresult is shown in Figs. 3 and 4, wherein the shaft 22' of the slider24' has mounted thereon a spoke-like abutment member 5|, each of thearms 52 of which has a different length, thereby providing a series ofdiffering transverse spacings for the abutment point 26.

As shown in Fig. 4 the shaft 22 is conveniently rotated by means of acrank 25', and is locked in preselected position by a knurled lock nut53. The plates 23' of the slider 24' are secured together in positionembracing the bar 13 by a pair of spacers 54 and 55, the bottom of thelatter being the surface providing a seat for the template l2 againstthe protractor bar 34. It will be understood that the slider 24 of Fig.1 appears in cross section much as shown in Fig. 4 for the slider 24'.

From the above description it will be seen that there has been describeda template for the checking of propeller blade pitch having practicallyuniversal application to all types of airplane propellers.

Obviously many modifications and variations of the present invention arepossible in the light of the above teachings. It is therefore to beunderstood that within the scope of the appended claims the inventionmay be practiced otherwise than as specifically described.

The invention described herein may be manufactured and used by or forthe Government of the United States of America for governmental purposeswithout the payment of any royalties thereon or therefor.

What is claimed is:

l. A propeller blade template comprising a bar having abutment meansadjacent one end thereof against which a propeller blade may abut, aslider slidable along said bar, said slider being comprised of a pair ofplates embracing said bar and protruding transversely therefrom andmeans connecting said plates to hold the slider to said bar, a shaftextending through a protruding portion of said plates, and an abutmentcam mounted on said shaft and rotatable about the axis thereof, wherebyone end of said bar may be spaced at selectively differing distancesfrom the blade.

2. A propeller blade template comprising a bar having abutment meansadjacent one end thereof against which a propeller blade may abut, aslider slidable along said bar, said slider including a pair of platesembracing said bar and protrucling transversely from each side thereofand means connecting said plates to hold the slider to said bar, a shaftextending through a protruding portion of said plates, a non-circularabutment member rotatably mounted on said shaft in edgewise relationthereto and having a plurality of points on its periphery adapted tobear against the blade and spaced at differing radii from said 7 screwthreaded thru one of said plates and operable to lock said slider inselected position along said bar, a shaft extending through a protrudingportion of said plates, an abutment cam mounted on said shaft androtatable about the axis thereof, whereby one end of said bar may bespaced at selectively differing distances from the blade, means forlocking said abutment cam in selected position to said slider, and a setscrew threaded thru the other protruding portion of one of said platesfor securing said bar to a protractor.

4. A propeller blade template comprising a, bar having means adjacentone end constituting a two pointabutment for a propeller blade to bemeasuredQa slider comprised of two plates circumjacent said bar withcross members securing said plates; together and permitting slidingmovement of said slider along said bar. a set screw threadedthru saidslider for clamping said slider to said bar at selected points, a shaftextending between said plates, a cam mounted on said shaft between saidplates and rotatable about-the shaft axis, a crank on one end of saidshaft having a detent pressed toward the adjacent plate, and a series ofcircumferentially spaced recesses adjacent said detent for providingdiscrete positioning points for said arm, and hence for said cam.

VASILI S. DRAKE.

References Cited in the file of this patent UNITED STATES PATENTS NumberName Date 412,984 Schmidt Oct. 15, 1889 10 1,206,060 Warner Nov. 28,1916 1,213,134 Fellows Jan. 16, 1917 1,509,703 Bourgeois Sept. 23, 19241,637,921 Simpson Aug. 2, 1927 1,736,247 Bodenlos Nov. 19, 1929 151,896,926 Von Frommer Feb. 7, 1933 2,238,782 Roche Apr. 15, 19412,343,802 Radney Mar. 7, 1944 2,358,987 MacKay Sept. 26, 1944 2,402,567Milner June 25, 1946 20 2,402,715 Warner June 25, 1946 FOREIGN PATENTSNumber Country Date 293,249 Germany July 24, 1916

